Packets crawled using snmp_exporter are in {}; how to solve the problem

[airsmon]

Host operating system: output of uname -a

snmp_exporter version: output of snmp_exporter -version

What device/snmpwalk OID are you using?

If this is a new device, please link to the MIB(s).

### What did you do that produced an error?
# HELP env4disensorIndex env4disensor System Entry Index.
# TYPE env4disensorIndex gauge
env4disensorIndex{env4disensorIndex="1"} 1
# HELP env4disensor_10_Fixed4DI01Door1 env4disensor_9_Fixed4DI01Door1 status.
# TYPE env4disensor_10_Fixed4DI01Door1 gauge
env4disensor_10_Fixed4DI01Door1{env4disensor_10_Fixed4DI01Door1="-9999"} 1
# HELP env4disensor_11_Fixed4DI01Door2 env4disensor_10_Fixed4DI01Door2 status.
# TYPE env4disensor_11_Fixed4DI01Door2 gauge
env4disensor_11_Fixed4DI01Door2{env4disensor_11_Fixed4DI01Door2="-9999"} 1
# HELP env4disensor_12_Fixed4DI01Water env4disensor_11_Fixed4DI01Water status.
# TYPE env4disensor_12_Fixed4DI01Water gauge
env4disensor_12_Fixed4DI01Water{env4disensor_12_Fixed4DI01Water="-9999"} 1

What did you expect to see?

What did you see instead?